OFFSET
6,3
FORMULA
G.f.: Sum_{k>=3} x^(k*(k + 1)/2) / Product_{j=1..k} (1 - x^j).
a(n) = A000009(n) - floor((n + 1)/2). - Vaclav Kotesovec, Sep 14 2021
MATHEMATICA
nmax = 60; CoefficientList[Series[Sum[x^(k (k + 1)/2)/Product[(1 - x^j), {j, 1, k}], {k, 3, nmax}], {x, 0, nmax}], x] // Drop[#, 6] &
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Sep 06 2021
STATUS
approved